Well I'm not sure if I totally agree. I think that the Shadow has often been seen to screw its self. I can't think of anything more satisfying than Rand preventing another taint on the One Power using the Dark One's own magic against him. I'm not saying it will happen, but thematically I don't see a problem. I'm not saying that Rand must be evil, but it could be similar to Verin infiltrating the BA to destroy them. Sometimes the Light gets to be smug too..

I don't agree. The text says that he suddenly becomes so black that he even soaks up the light of Callandor. Until then, the text clearly stated that he had no chance against Rand with the sa'angreal. It's a sign that he has suddenly gained equal footing, and its reflected in his triumphant look.

I agree with you that he was dreamwalking until then. Well, mostly. I think his initial attacks of balefire were channeled, but after that he travelled and most likely went to TAR where Rand chased after him. I think you probably could do all of those things with the OP if you had the aptitudes, but Ishamael is strong in TAR, its logical he'd go there if being chased by a strong channeler.

Apart from that, I'm not sure if you're contending that Ishamael used saidin mostly and had to beg for TP use? I find that completely unlikely. I think his appearance is more than evidence enough that he is an exclusive TP user and has been since the War of Power.

I guess he asked the DO to aid him directly. That's sort of like having your patron god come down and defend you.